Blood is one of the most useful samples in the medical diagnosis field. Generally, most analytical devices for use in diagnostic medicine are designed to react blood samples with reagents in quantitative manners and to analyze the results.
Accordingly, accurate measurements of sample quantities are physical factors which have direct influence on and make critical impact on the analytical results. Volumetric devices currently in use are precise to the microliter level and thus, measurement errors are so negligible as to have almost no effects on analytical results of samples present in milliliters.
However, when the total volume of a sample is as small as a microliter, such micro-level errors greatly affect the analysis results. For precise diagnosis with a microliter sample volume, therefore, the measurement errors must be decreased to a suitable level.
Most of the automatic precision pipetting devices developed thus far are precise enough to overcome the limitations encountered at the microliter level. However, these automatic precision pipetting devices are unsuitable for use in fields and on a small scale. The automatic devices may be economically advantageous when a great many samples are used in the laboratories. On the other hand, it is economically unfavorable to apply such an automatic device to only tens of samples. Further, the automatic devices are practically impossible to use in emergent situations.
A total volume of a microliter sample requires a measurement error of at least 0.1 μl or less in order to generate an accurate analysis result. It is very difficult to maintain an amount or volume of a sample at a constant level without a precision pipette when the quantity of the sample is very small.
Without a precision device, it is highly difficult to maintain the volumetric error within an allowable range when a sample has a total volume in the microliter range. Thus, when a sample is present in the microliter range a new technical problem arises.
In addition, after being taken in the field, a sample is pre-treated and transferred to a measurement machine in the laboratory. In the course of the sampling and transference, significant measurement error may be generated without the use of a precision pipette.